Conversion of hydrocarbon oils



Aug. 9, 1938. K. SWARTWOOD 2,126,229

CONVERSION OF HYDBOCARBON OILS Filed Feb. 15, 1957 49 FRACTIONATOR REACTION AND/0R SEPARATING 5 nzouczo PRESSURE l4 VAPORIZING 0R QOKING CHAMBER (ZONDEN SER 5 37 FRACTIONATOR CONDEN SER a2 33 I COOLING AND SEPARATING k 20m: ml

INVENTOR KENNETH SWARTWOOD TTO RNEY Patented Aug. 9, 1938 UNITED STATES PATENT OFFICE CONVERSION or HYDROCARBON OILS Application February 15, 1937, Serial No. 125,800

13 Claims.

This invention relates to the conversion of hydrocarbon oils and is more specifically concerned with an improved process for separately cracking selected fractions of both the hydrocarbon oil charging stock for the process and the intermediate liquid conversion products under independently controlled conditions, accompanied, when desired, by coking of the heavy liquid conversion products and high-boiling components of the charging stock.

As applied to the treatment of hydrocarbon oil charging stocks of relatively wide boiling range, such as crude petroleum or the like containing a substantial quantity of materials boiling within the range of gasoline, the invention offers an efficient and a simple process for fractionally distilling or topping the charging stock, cracking its low-boiling fractions, including any poor antiknock motor fuel components, to improve their antiknock value, cooling the resultant highly heated products suiiitciently to prevent any excessive cracking thereof and to remove therefrom undesirable high-boiling conversion products, by passing said heated products. in indirect heat exchange with said charging stock, whereby to supply to the latter at least a substantial portion of the heat required for its fractional distillation, fractionating the remaining vaporous components of said conversion products for the formation of reflux condensate and recovery of their desirable lower-boiling components, such as good quality gasoline, selectively cracking said reflux condensate and utilizing the resultant heated products for assisting further vaporization and, when desired, coking of the residual liquid products of the process, including any high-boiling components of the charging stock remaining unvaporized in the fractional distilling or topping step, subjecting vaporous products of the last mentioned cracking step, including vaporized components of said residual liquid products, to fractionation, either alone or together with said vaporous components of the first mentioned conversion products, separately cracking all or selected high-boiling fractions of the resultant reflux condensate and commingling the heated.

55, treatment and to produce the desired results.

These alternative methods will be more fully explained in connection with the following description of the accompanying diagrammatic drawing. i

The drawing illustrates one specific form of apparatus in which the various embodiments of the process of the invention may be conducted.

Heating coil I, to which relatively heavy oil is supplied, as will be later described, for cracking, is located within furnace 2 by means of which the oil passing through the heating coil is heated to the desired cracking temperature,

preferably at a substantial 'superatmospheric' pressure. The heated products are discharged from heating coil I through line 3 and valve 4 into an enlarged separating chamber 5.

Separation of vaporous and liquid conversion products is accomplished in chamber 5 and charging stock supplied to this zone, preferably in preheated state, as will be later. described, is cominingled with the heated products from heating coil I, substantially vaporized in this zone and separated, together with the conversion products, into vaporous and liquid fractions. Chamber 5 is preferably operated at a substantial superatmospheric pressure and preferably the charging stock is sufliciently heated, prior to its introduction to this zone, so that it does not reduce the temperature in chamber 5 below that at'which the charging stock is subjected to mild cracking under the superatmospheric pressure employed, whereby chamber 5 functions as a reaction zone wherein mild cracking of the charging stock and continued cracking of the conversion products from heating coil l, is accomplished. However, when desired, the temperature and pressure conditions employed in chamber 5 may be sufficiently low to preclude any appreciable continued cracking of the materials supplied to this zone from heating coil I and/or any appreciable cracking of the charging stock. This latter type of operation is ordinarily accomplished by supplying the charging stock to this zone sufficiently cool to give a resultant temperature in this zone below that at which cracking will occur at a substantial rate under the pressure conditions employed therein. In any case, however, the temperature-in chamber 5 is sufficiently high to effect the vaporization of, at least a substantial portion of the charging stock in this zone.

Liquid products, including any non-vaporous components of the charging stock, and/or liquid conversion products resulting from mild cracking of the charging stock in chamber 5, as well as liquid components of the conversion products from heating coil I, are removed from the lower portion of chamber 5, either alone or together with a minor portion of the vaporous materials, and directed through line 6 and valve 1 into vaporizing and separating chamber 8. Chamber 8 is preferably operated at a substantially reduced press-ure relative to that employed in chamber 5, by means of which appreciable further'vaporization of the liquid products supplied to this zone is accomplished, resulting in the formation of a relatively heavy residual liquid product in this zone which may be recoveredias such, by removing the same from the lower portion of the chamber through line 9 and valve In to cooling and storage, or elsewhere as desired, or which may,

when desired, be reduced to coke in this zone, preferably with the assistance of a heat carrying medium, supplied thereto as will be .later described. Vaporous products are withdrawn from th'e'upper portion of chamber 8 and directed through. line I2 and valve I3 to fractionation in fractionator I4.

Vaporous products, comprising the components of the conversion products supplied from heating coil I to chamber .5 and remaining vaporized in this zone, as well as any vaporous products resulting from mild cracking of the charging stock in this zone and any uncracked vaporous components of the charging stock, are removed from the upperportion of chamber 5 and directedtherefrom through line I5 and valve I6 to heating coil I1. Suflicient heat is supplied to the materials passing through heating coil H, by means'of furnace I8, to heat the same to the desired cracking temperature. Preferably this temperature is substantially above the temperature employed in chamber 5 and ordinarily also above the temperature employed in heating coil I. Ordinarily the pressure employed at the outlet fromheating coil II will be somewhat lower than that employed in chamber 5 in order that the vaporous products from the latter zone may be passed through the heating coil without the aid of a pump or compressor. However, it is within the scope of the invention to employ acompressor'in line I 5 and maintain a higher superatmo'spheric pressure in heating coil IT, or, instead of "supplyingvaporous products from chamber 5 directly to heating coil I 1, they may be first subjected to condensation, by well known means, not illustrated, and the resulting condensate supplied by pump to heating coil IT. The latter method, however, will either be wasteful from the standpoint of heat economy and/r involve the use of considerable additional equipment, such as heat exchanging, condensing, collecting and pumping equipment, and is, therefore, not the preferred method of operation.

The low-boiling oils supplied preferably in vaporous state to heating coil I! will comprise cracked products boiling within the range of gasoline, as well as any gasoline components of the charging stock which remain uncracked in chamber and will normally include somewhat higher boiling materials, such as heavy naphtha fractions, kerosene, kerosene distillate, light gas oil and the like, the particular nature of which willdepend to a large degree, so far as the endboiling point of the mixture is concerned, upon the temperature and pressure conditions employed in chamber 5, which in turn may be varied to suitrequirements.

-Preferably, the crackingconditions employed in heating coil I! are regulated to effect a substantial improvement in the quality of the gasoline supplied thereto with respect to its antiknock value and also to cracking higher boiling components of the mixture supplied to this zone for the production therefrom of additional yields of good quality gasoline. Preferably, since only relatively light oils are supplied to heat coil II, the size and type of heater selected for this stage of the system is such that substantially all of the desired cracking of this mixture may be accomplished in the heating coil, although, when desired, a succeeding reaction or digestion zone of any well known form, not illustrated, may be utilized, when desired, to provide additional con version time for the heated materials following their discharge from coil H.

In the particular case here illustrated, the highly heated products discharged from heating coil I! are directed through line I9 and valve to a suitable cooling and separating zone indicated at 2 I, wherein the heated products are cooled in any desired manner (one suitable method and means being later described) sufficiently to prevent any excessive continued conversion thereof and to separate therefrom, as condensate, high boiling components which are undesirable as cracking stock for any of the various heating coils of the system. Such heavy condensate is removed from the lower portion of chamber 2! through line 22 and valve 23 to pump 24 by means of which it is preferably returned through line 25 and valve 26 to chamber 5 for further treatment in this zone under the conditions employed therein, or it may, when desired, be supplied, all or in part, from line 25 through line 21 and valve 28 to chamber 8, or it may be directed, all or in part, to chamber 8 by commingling the same by well known means, not illustrated, with the stream of oil passing from chamber 5 through line 6 and valve 1 into chamber 8. Components of the heated products from heating coil I! which remain uncondensed in chamber 2I are withdrawn therefrom through line 44 and may be directed therefrom either through line 45 and valve 46 to fractionator I4, or through valve 41 in line 44 to separate fractionation in fractionator 48.

Hydrocarbon oil charging stock for the system, which is preferably an oil of relatively wide boiling range, such as crude petroleum containing gasoline or gasoline fractions of unsatisfactory antiknock value, but which may comprise any desired type of oil, is supplied through line 3| and valve 32 to charging pump 33 wherefrom it is directed through line 34 and may pass through valve 35 in this line into chamber 2I wherein it passes through a suitable heat transfer means, such as a nest of tubes or closed coil, indicated at 3B, in indirect heat exchange with the heated products supplied to this zone, as previously described, from heating coil Il. The thus preheated charging stock is directed from chamber 2| through line 3'! and valve 38 to be supplied therefrom to chamber 5 at any desired point or plurality of points in this zone, provision being made in the case here illustrated for directing all or a portion of the same into the lower portion of chamber 5 through line 39 and valve 44] and for supplying a portion or all of the charging stock into the upper portion of the chamber by means ofvalve 4| in line 3i and line 3. Provision is also made for by-passing a portion or all of the charging stock, when desired, around chamber 2I by means of line 42 and valve 43, communicating with lines 34 and 31.

The vaporous products supplied to fractionator M as previouslydescribed, which may comprise only vaporous products from chamber 8, or, when desired, vaporous products from chambers 8 and 2|, are subjected to fractionation in this zone,

whereby their components boiling above the range of the desired final light distillate product are condensed as reflux condensate. Fractionated vapors of the desired end-boiling point are withdrawn together with normally gaseous products from the upper portion of fractionator l4 and directed through line 49 and valve 50 to condensa tion and cooling in con-denser 5|. The resulting distillate and uncondensed gases pass through line 52 and valve 53 to collection and separation in receiver 54. The uncondensed gases are released from the receiver through line 55 and valve 7 55. The distillate is withdrawn from receiver 54 through line 51 and valve 58 to storage or to any desired further treatment.

When desired regulated quantities of the distillate collected in receiver 54 may be recirculated, by well known means, not illustrated, to the upper portion of fractionator M to serve as a cooling and refluxing medium in this zone.

The total reflux condensate formed in fractionator l4 may, when desired, be directed from the lower portion of this zone through line 58 and valve 5! to pump" 62, to be supplied therefrom through line 63 and valve 54 to heating coil I for cracking'therein, as previously described, or, when desired, the reflux condensate may be separated into selected relatively low-boiling and high-boiling fractions. In the latter case only the highboiling fractions are supplied, as described, to

3 5" heating coil I, while the selected lower boiling fractions are withdrawn from one or a plurality of suitable intermediate points in the fractionator, provision being made, in the case here illustrated, for directing the same from fractionator i4 through line 66 and valve 61 to pump 68 wherefrom they are directed through line 59, Valve and line H to further cracking in heating coil 12, as will be later described.

When fractionator 48 is employed for separate fractionation of the vaporous products from chamber 2!, their components boiling above the range of the final light distillate product of this stage of the system are condensed in this zone as reflux condensate which is withdrawn from the lower portion of the fractionator through line 13 and valve 14 to pump 15. Pump l5 may supply the reflux condensate through line H and valve 15 to conversion in heating coil 12 or it may be directed from line H through line 11, valve 78 andline 63 to conversion in heating coil I. Ordinarily, when fractionator 48 is employed, the reflux condensate from this zone will be subjected to further cracking in heating coil 12 and the total reflux condensate from fractionator M will be subjected to cracking in heating coil l, although alternative methods of operation afforded by the facilities shown in the drawing may be advantageous in certain instances.

, Fractionated vapors of the desired end-boiling point are withdrawn together with normally gaseous products from the upper. portion of fractionator 48, when this zone is utilized, and are directed through line 80 and valve 8! to condensation and cooling in condenser 82. The resulting distillate passes through line 83 and valve 84 to collection and separation in receiver 85. The uncondensed gases may be released from receiver 85 through line 85 and valve Bl. Distillate is withdrawn from receiver 85 through line 88 and valve 89' to storage or to any desired further treatment.

When desired, regulated quantities of the distillate collected in receiver 85 may be recirculated by well known means, not illustrated, to the upper portion of fractionator 48 to serve as a cooling and refluxing medium in this zone.

The preferred range of operating conditions which may be employed in an apparatus such as illustrated and above described to accomplish the desired results may be approximately as follows: The first mentioned heating coil, to which the total or high-boiling fractions of the reflux con.- densate formed in fractionator M are supplied, may employ an outlet conversion temperature ranging, for example, from 850 to 950 F. or thereabouts, preferably with a substantial superatmospheric pressure, as measured at the outlet from the heating coil, of from 100 to 500 pounds or more per square inch. The succeeding separating chamber to which the products from this heating coil are supplied, preferably, as previously mentioned, also utilizes a substantial superatmospheric pressure which may be substantially the same or lower than that employed in the communicating heating coil. The average temperature maintained in this chamber may range, for example, from 600 to 900 F. or thereabouts, depending upon the degree to which the charging stock is preheated prior to its introduction into this zone and to the extent to which it is desired to crack the charging stock and the desired nature of the materials to be subjected to further cracking in heating coil ll. Heating coil H, depending upon the nature of the material supplied thereto from chamber 5 and the desired results, may utilize an outlet conversion temperature ranging, for example, from 900 to 1100 F. or thereabouts, with any desired pressure in this zone ranging from substantially the same as that employed in chamber 5 down to substantially atmospheric pressure. A higher pressure than that employed in chamber 5 may, of course, be utilized in heating coil I8, in case a vapor pump or corn pressor is utilized to maintain the desired differential, or in case the cracking stock for heating coil 1 7 is supplied thereto by pump in liquid state. The conversion products from heating coil I? are preferably cooled, prior to fractionation of their vaporous components, to a temperature of the order of 650 to 850 F. or thereabouts. The conversion temperature employed at the outlet of heating coil l2, when this zone is utilized, may range, for example, from 900 to 1000 F. or thereabouts and it may employ any desired pressure from 1000 pounds or thereabouts per square inch, down to substantially the same pressure as that employed in the reduced pressure vaporizing or coking chamber 8, to which the heated products from this zone are supplied, although a superatmospheric pressure of. the order of 200 to 800 pounds or thereabouts per square inch is preferred at the outlet from heating coil 72. The pressure employed in chamber 8, preferably, as previously mentioned, is substantially lower than that employed in chamber 5 and may range, for example, from 100 pounds, or thereabouts, per square inch, down to substantially atmospheric pressure. The fractionating, condensing and collecting equipment may employ pressures substantially the same or somewhat lower than. the pressure maintained in the preceding portions of the system communicating therewith which employ the lowest pressure.

As a specific example of one of the many possible operations which may be conducted in accordance with the process of the invention and in an apparatus such as illustrated and above described, the charging stock is a California crude of approximately 22 A. P. I. gravity having an initial boiling point of about 180 F., containing approximately of material boiling up to 350 F., approximately 13% at 437 F. and approximately 35% at 572 F. This material is preheated to a temperature of approximately 835 F., the heat being obtained in part by indirect heat exchange with the heated products from the vapor cracking coil and in part by further direct heating by the charging stock prior to its introduction into the reaction and separating chamber. A temperature of approximately 950 F. and a superatmospheric pressure of approximately 350 pounds per square inch, is employed at the outlet from heating coil I and an average temperature of approximately 850 F. is maintained in the reaction and separating chamber. Liquid products are supplied from the reaction chamber to acoking zone which is operatedat a superatmospheric pressure of approximately 100 pounds per square inch. Vaporous products from the reaction chamber are heated in coil I! to an outlet temperature of approximately 1000 F. at a superatmospheric pressure, measured at the outlet from this zone, of approximately 150 pounds per square inch. The products from this zone are partially cooled by indirect heat exchange with the charging stock, the resulting condensate being supplied to the coking zone and the remaining uncondensed vapors directed to the same fractionator to which vaporous products from the coking zone are supplied. Only high-boiling fractions of the reflux condensate from this fractionator are returned to heating coil I, while selected lower-boiling fractions, containing approximately 3% of material boiling up to 400 F. and having an endboiling point of approximately 570 F., are heated in coil 12 to an outlet conversion temperature of approximately 975 F. at a superatmospheric pressure of about 600 pounds per square inch, the resulting highly heated products being introduced into direct contact with the materials undergoing coking in the coking zone. This operation will produce, per barrel of charging stock, approximately 63% of 400 F. end-point gasoline having an octane number of better than 70 by the motor method and approximately 80 pounds of good quality coke suitable as domestic fuel, the remainder being chargeable principally to gas and loss.

I claim as my invention:

1. In a process for the pyrolytic conversion of hydrocarbon oils, wherein an oil of relatively high-boiling characteristics recovered from within the system as later described, is cracked at cracking temperature and superatmospheric pressure in a heating coil, the heated products introduced into an enlarged separating chamber also maintained at superatmospheric pressure, wherein separation of vaporous and liquid conversion products is accomplished, said liquid products supplied to a zone of substantially reduced pressure wherein their appreciable further vaporization is effected, the resultant evolved vapors subjected to fractionation for the formation of reflux condensate, fractionated vapors of the desired end-boiling point condensed, the resulting distillate recovered and reflux condensate formed by said fractionation supplied, as said oil of relatively high-boiling characteristics, to the heating coil for cracking, the improvement which comprises separately removing vaporous products from said enlarged separating zone, cracking the same in'a separate heating coil maintained at higher temperature than that employed in the first mentioned heating coil, passing the resultant highly heated products in indirect heat exchange with hydrocarbon oil charging stock for the process, whereby to heat the charging stock sufficiently to eifect substantial vaporization thereof and whereby to cool said heated products sufiiciently to prevent their excessive further cracking and to remove therefrom, as condensate, undesirable high-boiling components, supplying the thus heated charging stock and said condensate to said enlarged separating zone,

subjecting the components of said heated products which remain uncondensed by said heat exchange to fractionation for the formation of reflux condensate and to recover therefrom desirable low-boiling components, subjecting reflux condensate formed by said fractionation of the last mentioned vapors to further cracking in another separate heating coil, and introducing resultant highly heated products into the said zone of substantially reduced pressure.

2. A process such as defined in claim 1 wherein high-boiling non-vaporous components of the materials supplied to said zone of substantially reduced pressure are reduced therein to coke.

3. A process such as defined in claim 1 wherein high-boiling non-vaporous components of the materials supplied to said zone of substantially reduced pressure are reduced therein to coke with the assistance of said heated products from the last mentioned heating coil.

4. In a process for the pyrolytic conversion of hydrocarbon oils, wherein an oil of relatively high-boiling characteristics, formed as later described, is cracked at cracking temperature and superatmospheric pressure in a heating coil, resultant heated products supplied to an enlarged separating zone also maintained at superatmospheric pressure, wherein separation of vaporous and liquid products is accomplished, said liquid products supplied to a zone of substantially reduced pressure wherein they are appreciably further vaporized and the resultant evolved vapors subjected to fractionation, the improvement which comprises separately removing vaporous products from said enlarged separating zone, cracking the same in a separate heating coil maintained at higher temperature than that employed in the first mentioned heating coil, passing highly heated products resulting from the last mentioned cracking operation in. indirect heat exchange with hydrocarbon oil charging stock for the process, whereby to cool said heated products sufficiently to prevent excessive further cracking thereof and to remove therefrom, as condensate, desirable high-boiling components, introducing said condensate and resultant heated charging stock into said enlarged separating chamber, subjecting components of the last mentioned conversion products which remain uncondensed by said heat exchange to said fractionation together with the vapors resulting from said further vaporization of said liquid products, separating reflux condensate formed by said fractionation into selected relatively low-boiling and high-boiling fractions, supplying the latter as said oil of relatively high-boiling characteristics to the first mentioned heating coil for cracking, separately cracking selected low-boiling fractions of the reflux condensate in another separate heating Lil coil, introducing heated products of the last mentioned cracking step into said zone of substantially reduced pressure to commingle therein with said liquid products and assist their vaporization, subjecting fractionated Vapors of the desired endboiling point to condensation, and recovering the resulting products.

5. A process such as defined in claim 4 wherein high-boiling non-vaporous components of the materials supplied to said zone of substantially reduced pressure are reduced therein to coke.

6. A process such as defined in claim 4 wherein high boiling non-vaporous components of the materials supplied to said zone of substantially reduced pressure are reduced therein to coke'with the assistance of said heated products from the last mentioned heating coil.

7. A process for the treatment of hydrocarbon oils which comprises introducing charging stock for the process, comprising an oil of relatively wide boiling range, into a vaporizing and separating chamber maintained at superatmospheric pressure, wherein it is separated into low-boiling vaporous and high-boiling liquid fractions, simultaneously cracking an oil of relatively high-boiling characteristics, recovered from within the system as will be later described, in a heating coil maintained at cracking temperature and superatmospheric pressure, introducing the resultant heated products into said vaporizing and separating chamber, wherein they are separated into vaporous and liquid fractions, together with said charging stock, separately removing said vaporous and liquid fractions from the vaporizing and separating chamber, passing said vaporous fractions through a separate heating coil wherein they are cracked at higher temperature than that maintained in the first mentioned heating coil, cooling the resultant heated products sufficiently to prevent their excessive further cracking and to remove undesirable high-boiling components there from as condensate, subjecting the remaining vapors to fractionation, supplying said liquid fractions removed from the vaporizing and separating chamber to a zone of substantially reduced pressure wherein appreciable further vaporization thereof is effected, subjecting vapors evolved in said zone of substantially reduced pressure tov said fractionation together with said remaining vapors, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resultant distillate, supplying a reflux condensate formed by said fractionation of the vaporous products, as said oil of relatively highboiling characteristics, to the first mentioned heating coil for cracking, supplying a separate reflux condensate formed by said fractionation of the vaporous products to a separate heating coil wherein'it is cracked at a temperature intermediate that employed in the first and second mentioned heating coils, and introducing resultant heated products into said zone of substantially reduced pressure;

8. A process such as defined in claim '7 wherein said liquid fractions are reduced to coke in said zone of substantially reduced pressure.

9. A process for the treatment of hydrocarbon oils which comprises introducing charging stock for the process, comprising an oil of relatively wide boiling range, into a vaporizing and separating chamber maintained at superatmospheric pressure, wherein it is separated into low-boiling vaporous and high-boiling liquid fractions, simultaneously cracking an oil of relatively highboiling characteristics, recovered from within the system as will be later described, in a heating coil maintained at cracking temperature and superatmospheric pressure, introducing the resultant heated products into said vaporizing and separating chamber wherein they are separated into vaporous and-liquid fractions, together with saidcharging stock, separately removing said vaporous and liquid fractions from the vaporizing and separating chamber, passing said vaporous fractions through a separate heating coil wherein they are cracked at higher temperature than that maintained in the first mentioned heating coil, cooling the resultant heated products sufficiently to prevent their excessive further cracking and to remove undesirable highboiling components therefrom as condensate, subjecting the remaining vapors to fractionation, supplying said liquid fractions removed from the vaporizing and separating chamber to a zone of substantially reduced pressure wherein appreciable further vaporization thereof is effected,,subjecting vapors evolved in said zone of substantially reduced pressure to said fractionation together with said remaining uncondensed vapors of the second mentioned cracking g.

operation, subjecting fractionated vapors of the desired end-boiling point to condensation, recovering the resultant distillate, separating reflux condensate formed by said fractionation into selected relatively low-boiling and high-boiling fractions, supplying the latter, as said coil of relatively high-boiling characteristics, to the first mentioned heating co-il for cracking, separately cracking selected low-boiling fractions of said reflux condensate in another separate heating coil, and introducing highly heated products from the last mentioned heating coil into said zone of substantially reduced pressure.

10. A process such as defined in claim 9 wherein said liquid products are reduced to coke in said zone of substantially reduced pressure with the assistance of said highly heated products supplied to this zone from the last mentioned heating coil.

11. A process such as defined in claim 9 wherein said condensate resulting from cooling of the heated products of the second mentioned cracking operation is returned to said vaporizing and separating zone.

12. A process such as defined in claim 9 wherein said charging stock contains an appreciable quantity of materials of poor antiknock value boiling within the range of gasoline which are supplied from said vaporizing and separating chamber to the second mentioned cracking step, wherein they are cracked to produce materials within the boiling range of motor fuel of substantially improved antiknock value.

13. A hydrocarbon oil conversion process which comprises heating reflux condensate to cracking temperature under pressure in a heating coil and introducing the resultant products to a separating chamber maintained under pressure, in-

troducing charging oil for the process to said chamber and therein vaporizing a substantial portion thereof, separating Vapors from unvaporized oil in the chamber and discharging the unvaporized oil into a vaporizing chamber maintained under lower pressure than the separating chamber, separately removing vapors from the separating chamber and heating the same to higher cracking temperature than the reflux condensate in the heating coil, fractionating resultant vaporous conversion products to condense heavier fractions thereof, subjecting reflux same independently of said vaporous conversion condensate'formed by this fractionation to indeproducts to form a second reflux condensate, pendently controlled cracking conditions in a supplying this second reflux condensate to the second heating coil and then discharging the first-mentioned heating coil, and finally consame into contact with the unvaporized oil in densing the fractionated vapors.

the vaporizing chamber, removing vapors from I the vaporizing chamber and fractionating the KENNETH SWARTWOOD. 

